Secondary products of concrete are obtained by mixing materials including a cement, an aggregate, water, and a dispersant, molding in various forms, and curing. For these concretes, it is important to exhibit high strength early thereof from the viewpoint of productivity, or for enhancing the turnover rate of a form, because the form is repeatedly used many times. For this purpose, measures are taken, including (1) using a high early strength portland cement as a cement, (2) using various polycarboxylic acid compounds as an admixture to reduce the water content in the cement composition, and (3) steam curing the concrete.
Japanese Patent Publication JP-A No. 64-83544 describes a quick curing cement composition comprising a quick curing cement, polyol, and oxycarboxylic acid or a salt thereof. Japanese Patent Publication JP-A No. 2006-282414 describes a strength-improving agent for cement, comprising glycerol or a derivative thereof and a polycarboxylic acid copolymer at a specific ratio.
The current demands for further increased productivity and the like include a more shortened step of curing. For example, in production of some concrete products, concrete is required to exhibit high strength only for 8 or 24 hours of curing time. A general step of curing includes complicated operations such as heating with steam. The step is thus desirable to be shortened and simplified. It is also very commercially desirable to omit curing with steam.
It is also desirable to omit steam curing for reducing energy consumption, because of the large energy cost due to use of steam.
Japanese Patent Publication (JP-A) No. 06-19955 discloses that a combination of an accelerator and a low molecular weight glycol accelerates curing. Japanese Patent Publication JP-A 2008-519752 discloses that a raw glycerol improves compression strength. WO-A2011/081115, published on Jul. 7, 2011, discloses a hardening accelerator comprising glycerol and an alkali metal sulfate or thiosulfate. WO-A2009/119897 discloses a hardening accelerator comprising a glycol ether compound or a glycerol derivative, and optionally a phosphate ester polymer. WO-A2009/119893 discloses an additive comprising a copolymer and a glycol ether compound or a glycerol derivative. WO-A2010/008093 discloses a hardening accelerator comprising a reaction product of a polyhydric alcohol or an alkylene oxide-adduct thereof with a sulfating agent.